题目

1/2+1/6+1/12+1/20+1/30+1/42的简便计算

提问时间：2020-07-25

答案

=1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7=6/7